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The STUDIA UNIVERSITATIS BABEŞ-BOLYAI issue article summary
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Abstract: Protists constitute an important component of microbial communities in the aquatic ecosystems. In microbial food webs phototrophic protists produce organic matter utilized by heterotrophic bacteria as food. Some phototrophic protists secrete substances suppressing bacterial growth or modulating bacterial quorum sensing. Heterotrophic protists consume prokaryotes changing their abundance and diversity. The effects of interactions between protists and prokaryotes are poorly understood in the hypersaline environments. The aim of the study was to characterize the prokaryotic communities associated with cultures of heterotrophic and phototrophic protists, using high-throughput sequencing. We used nine cultures of protists isolated from inland saline lakes (Orenburg region, Russia) and stored for years under laboratory conditions at 150 or 200‰ salinities. Phototrophic protists were represented by genera of green algae Dunaliella and Asteromonas, whereas heterotrophic protists belonged to the Heterolobosea group. Sequencing of 16S rRNA gene amplicons using MiSeq (Illumina) revealed that the prokaryotic communities associated with the heterotrophic protists were more diverse than those in association with the phototrophic protists. Only two classes, Gammaproteobacteria and Halobacteria, represented by a few genera, were found in all the cultures of phototrophic protists. Here, Halorubrum spp. and Halovibrio spp. were the most abundant genera. Gammaproteobacteria, Halobacteria, Sphingobacteriia, Deltaproteobacteria, Alphaproteobacteria classes, and Nanohaloarchaeota phylum were associated with halophilic heterotrophic protists. The obtained results suggest that taxonomic composition of associated halophilic prokaryotic communities differs drastically in cultures of phototrophic and heterotrophic protists.
Keywords: diversity, halophilic microbial community, high-throughput sequencing, protists |
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